Survival probabilities of white oak (Quercus alba) in small circular group and single tree openings ranging in size from 0.001 to 0.175 ha twelve years after opening creation are presented. At the ...beginning of the study, 3948 advance reproduction white oak trees were measured and tagged to determine survival of each tagged seedling at the end of the study. Logistic regression indicated that variables important in predicting advance reproduction survival included initial seedling basal diameter, aspect, slope, canopy opening size, opening border tree height and treatment for control of understory competition. Survival probability ranged from 10% to 90% depending on the combination of and disposition of variables. For these small openings, the greatest probability of survival of advance reproduction resulted when advance reproduction initial basal diameters were ≥1 cm, when the height of trees bordering the openings were relatively short, with understory chemical competition control, in the largest canopy openings, on 6% slopes, and on southwest and northwest aspects. These criteria can help managers select sites and treatment options for group opening creation that provide optimal conditions for advance reproduction survival.
•Oak decline and mortality were mainly controlled by tree characteristics.•Regional variations in oak mortality were related to ecoregions and historical forest conditions.•Recurrent droughts and ...disturbances trigger oak decline, but fire helps mitigate oak mortality.•Oak risk groups and annual survival rates can be used for prioritizing mitigation treatments.
During recent decades there has been widespread oak decline and mortality in the Missouri Ozarks, USA. We extracted data of 18,403 oak trees measured during 1999–2019 from the US Forest Service’s Forest Inventory and Analysis (FIA) database to examine the spatiotemporal patterns of oak decline and mortality and associated risk factors. The Missouri Ozarks were classified into three spatial clusters with low (<1.0%), moderate (1.0–1.5%) and high (>1.5%) annual oak mortality rates using kernel smoothing and the Jenks natural breaks method. Oaks within each spatial cluster were further divided into four, five and three risk groups respectively with differentiated annual mortalities (0.35%–3.05%) using a classification and regression tree model. The Kaplan-Meier survival analyses showed that oak trees from individual spatial clusters and risk groups responded differently to droughts, a major regional or sub-regional inciting factor of oak decline. Droughts could have a three to nine year lagged impact on tree mortality in the high risk groups, whereas had little effect on oak mortality in the low risk groups. Tree species, crown class, and stand age were the regionwide predisposing factors of oak decline. However, localized disturbances and geographic/vegetation conditions (e.g., drought, fire, insects, aspect, elevation, ecoregions, historical forest types) could either incite or alleviate the decline process and the fate of declining trees depending on the differentiated spatial clusters or risk groups. Resource managers can base associated risk factors and spatial clusters to rank risk levels to prioritize and plan management activities to mitigate oak decline and mortality.
LANDIS PRO predicts forest composition and structure changes incorporating species-, stand-, and landscape-scales processes at regional scales. Species-scale processes include tree growth, ...establishment, and mortality. Stand-scale processes contain density- and size-related resource competition that regulates self-thinning and seedling establishment. Landscapescale processes include seed dispersal and disturbances. LANDIS PRO is designed to be compatible with forest inventory data, thus extensive inventory data can be directly utilized to initialize and calibrate model parameters before predicting future forest changes. LANDIS PRO allows for exploring the effects of disturbances, management, climate change, and modeling the spread of invasive species. We demonstrate that LANDIS PRO successfully predicts forest successional trajectories and stand development patterns in the Central Hardwood Forest region in U.S.
Demographic processes (fecundity, dispersal, colonization, growth, and mortality) and their interactions with environmental changes are not well represented in current climate-distribution models ...(e.g., niche and biophysical process models) and constitute a large uncertainty in projections of future tree species distribution shifts. We investigate how species biological traits and environmental heterogeneity affect species distribution shifts. We used a species-specific, spatially explicit forest dynamic model LANDIS PRO, which incorporates site-scale tree species demography and competition, landscape-scale dispersal and disturbances, and regional-scale abiotic controls, to simulate the distribution shifts of four representative tree species with distinct biological traits in the central hardwood forest region of United States. Our results suggested that biological traits (e.g., dispersal capacity, maturation age) were important for determining tree species distribution shifts. Environmental heterogeneity, on average, reduced shift rates by 8% compared to perfect environmental conditions. The average distribution shift rates ranged from 24 to 200myear−1 under climate change scenarios, implying that many tree species may not able to keep up with climate change because of limited dispersal capacity, long generation time, and environmental heterogeneity. We suggest that climate-distribution models should include species demographic processes (e.g., fecundity, dispersal, colonization), biological traits (e.g., dispersal capacity, maturation age), and environmental heterogeneity (e.g., habitat fragmentation) to improve future predictions of species distribution shifts in response to changing climates.
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•Effects of biological traits and heterogeneity on species distribution shifts were investigated.•Biological traits were important for determining tree species distribution shifts.•Environmental heterogeneity slowed down tree species distribution shifts.•Shift rates of tree species were low and may not able to keep up with climate change.•Distribution models should include demography and heterogeneity to improve shift predictions.
Climate warming directly affects insect disturbance regimes by altering temperature‐dependent population development. Indirect effects of climate change on insect disturbance may mediate or ...accelerate direct effects via vegetation feedback (e.g. host tree demographic dynamics). However, such indirect effects have rarely been incorporated in predicting insect disturbance regimes.
We included both direct and indirect effects in a forest landscape modelling framework to simulate red oak borer ROB, Enaphalodes rufulus (Coleoptera: Cerambycidae) disturbance regimes under a warming climate from 2000 to 2150 in the Central Hardwood Forests, U.S. We quantified effect sizes and relative importance of direct effects and indirect effects of warming climate on the ROB disturbance using a factorial experimental design and two‐way ANOVA.
Both direct and indirect effects acted positively in the short and medium term (e.g. 0–100 years) while the effect size of indirect effects changed over time from positive (+30.9 kha) to negative (−17.3 kha) and mediated the positive direct effects in the long term (e.g. 100–150 years).
Direct effects had greater influence than indirect effects on ROB disturbed areas in the short term (e.g. <50 years), whereas indirect effects were more important (ω2 = 0.38 vs. 0.26) in the long term. This was because the host tree abundance significantly declined over time under warming climates, which decreased the forest susceptibility to ROB and thus overrode the outbreak‐promoting effects of warming climates in the long term.
Synthesis and applications. This study reveals indirect effects of warming climates mediate direct effects on insect disturbance regimes by altering primary host tree demographic dynamics. We highlight that indirect effects are important in understanding insect disturbance regimes under warming climates as they may mediate or even reverse the expectation of increased insect disturbance. Long‐term predictions of insect disturbance without considering indirect effects may overestimate its impacts under warming climates. Our findings also indicate that different management interventions are required at different time‐scales to maintain oak forests' health and sustainability in the U.S. central temperate broadleaf forests.
This study reveals indirect effects of warming climates mediate direct effects on insect disturbance regimes by altering primary host tree demographic dynamics. We highlight that indirect effects are important in understanding insect disturbance regimes under warming climates as they may mediate or even reverse the expectation of increased insect disturbance. Long‐term predictions of insect disturbance without considering indirect effects may overestimate its impacts under warming climates. Our findings also indicate that different management interventions are required at different time‐scales to maintain oak forests' health and sustainability in the U.S. central temperate broadleaf forests.
Temperate forests regrowing from historical land use and land cover change in the eastern US serve as carbon (C) sinks. Environmental drivers have been significantly altered (e.g. rising atmospheric ...CO2 concentration, warmer temperature, and elevated nitrogen (N) deposition) and will have a wide range of impacts on future forest C sinks. However, the interactions among these environmental drivers are unclear and their effects are subject to uncertainty. We assessed the combined and interactive effects of rising CO2 concentration, climate change (temperature, precipitation), and N deposition on forest aboveground net primary production (ANPP) and their relative contribution to ANPP changes of a temperate forest in the eastern US. We used a process-based ecosystem model PnET-day to simulate coupled cycles of C, water, and N of forest ecosystems. We found that (1) climate change exerted negative effects on ANPP (−0.250 kg C m−2 yr−1) whereas rising CO2 and N deposition enhanced ANPP (+0.253, +0.014 kg C m−2 yr−1); (2) climate change interacted with rising CO2 and N deposition to decrease ANPP (−0.032, −0.018 kg C m−2 yr−1); rising CO2 and N deposition acted in synergy to increase ANPP (+0.014 kg C m−2 yr−1); (3) changes in ANPP were mainly attributed to rising CO2 and climate change whereas N deposition effects and any two- or three-factor interactive effects were relatively small. Our results suggest that the total negative effect sizes will not be offset by the total positive effect sizes, thus resulting in reductions in forest ANPP over the 21st century.
Nonnative invasive plant species (NNIPS) cause significant damage to the native forest ecosystems in the southern United States forestlands, such as habitat degradation, ecological instability, and ...biodiversity loss. Taking the state of Alabama as an example, we used more than 5,000 permanent United States Department of Agriculture-Forest Service's Forest Inventory and Analysis (FIA) plots measured between 2001 and 2019 over three measurement cycles to test the suitable modeling unit for quantifying invasion patterns and associated factors for regional NNIPS monitoring and management. NNIPS heavily infest Alabama's forestlands, and forestlands plagued with at least one NNIPS have increased over time: 41.1%, 50.8%, and 54.8% during the past three measurements. Lonicera japonica (Thunb.) was the most abundant NNIPS in Alabama, with at least 26% of its forested lands infested. The FIA data were aggregated with multiple spatial units: five levels of hydrological units, three levels of ecological units, and a county level. Invasion indices were calculated for all spatial units based on NNIPS' presence/absence and average cover in each plot. The best modeling unit was identified based on Moran's test, with the county-level modeling unit providing the best Moran's I value over all measurement periods. Influencing factors of invasion were evaluated based on spatial lag models. Our models show that the invasion index decreased with increases in public forest areas in a county. In contrast, the human population density of neighboring counties positively influenced the invasion index.
Oak decline is a process induced by complex interactions of predisposing factors, inciting factors, and contributing factors operating at tree, stand, and landscape scales. It has greatly altered ...species composition and stand structure in affected areas. Thinning, clearcutting, and group selection are widely adopted harvest alternatives for reducing forest vulnerability to oak decline by removing susceptible species and declining trees. However, the long-term, landscape-scale effects of these different harvest alternatives are not well studied because of the limited availability of experimental data. In this study, we applied a forest landscape model in combination with field studies to evaluate the effects of the three harvest alternatives on mitigating oak decline in a Central Hardwood Forest landscape. Results showed that the potential oak decline in high risk sites decreased strongly in the next five decades irrespective of harvest alternatives. This is because oak decline is a natural process and forest succession (e.g., high tree mortality resulting from intense competition) would eventually lead to the decrease in oak decline in this area. However, forest harvesting did play a role in mitigating oak decline and the effectiveness varied among the three harvest alternatives. The group selection and clearcutting alternatives were most effective in mitigating oak decline in the short and medium terms, respectively. The long-term effects of the three harvest alternatives on mitigating oak decline became less discernible as the role of succession increased. The thinning alternative had the highest biomass retention over time, followed by the group selection and clearcutting alternatives. The group selection alternative that balanced treatment effects and retaining biomass was the most viable alternative for managing oak decline. Insights from this study may be useful in developing effective and informed forest harvesting plans for managing oak decline.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Aim
Population dynamics and disturbances have often been simplified or ignored when predicting regional‐scale tree species distributions in response to climate change in current climate‐distribution ...models (e.g., niche and biophysical process models). We determined the relative importance of population dynamics, tree harvest, climate change, and their interaction in affecting tree species distribution changes.
Location
Central Hardwood Forest Region of the United States.
Major taxa studied
Tree species.
Methods
We used a forest dynamic model, LANDIS PRO that accounted for population dynamics, tree harvest, and climate change to predict tree species’ distributions at 270 m resolution from 2000 to 2300. We quantified the relative importance of these factors using a repeated measures analysis of variance. We further investigated the effects of each factor on changes in species distributions by summarizing extinction and colonization rates.
Results
On average, population dynamics was the most important factor affecting tree species distribution changes. Tree harvest was more important than climate change by 2100 whereas climate change was more important than harvest by 2300. By end of the 21st century, most tree species expanded their distributions irrespective of any climate or harvest scenario. By 2300, most northern, some southern, and most widely distributed species contracted their distributions while most southern species, some widely distributed species, and few northern species expanded their distributions under warmer climates with tree harvest. Harvest accelerated or ameliorated the contractions and expansions for species that were negatively or positively affected by climate change.
Main conclusions
Our results suggest that population dynamics and tree harvest can be more important than climate change and thus should be explicitly included when predicting future tree species’ distributions. Understanding the underlying mechanisms that drive tree species distributions will enable better predictions of tree species distributions under climate change.
Dry-mesic old-growth oak forests are widely distributed remnants across the eastern U.S. and are expected to increase in number and extent as second-growth forests mature. In this study, we ...synthesize published and unpublished information to better define the species, structure and extent of these forests. Mean site tree density for trees ≥10 cm dbh ranged from 341–620 trees ha−1. In the eastern part of the region, most stand basal areas were >23 m2 ha−1, compared to ≤23 m2 ha−1 in the westernmost stands. Overall, woody species diversity was relatively low compared to old-growth oak forests on moister sites, with tree species per forest ranging from 5–18. The most common species among the stands were white oak (Quercus alba), northern red oak (Quercus rubra), and black oak (Quercus velutina). Shrub and vine species per forest ranged from 1–10, with common species or genera including Virginia creeper (Parthenocissus quinquefolia), poison ivy (Toxicodendron radicans), Vaccinium spp., and grapevines (Vitis spp.). Within the southern Appalachian Mountains, rosebay rhododendron (Rhododendron maximum) and mountain laurel (Kalmia latifolia L.) were common. Herbaceous species per stand ranged from 4–51, with the highest richness occurring in a southern Appalachian oak-hickory forest. The maximum within-stand age of the large trees ranged from 170 to over 365 years. The mean density of standing dead trees ≥10 cm dbh ranged from 31–78 ha−1 and the volume of coarse woody debris ≥10 cm in diameter averaged 52 m3 ha−1. We more fully describe the characteristics of these forests and fill gaps in the collective knowledge of this increasingly important forest type. However, over the past 20 years, there has been scant research on these forests, and older research studies have used a variety of research plots and methods. A uniform approach to surveying these sites is needed to gain a better understanding of these forests before we are faced with caring for an increase in old-growth forest areas.
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